linux-cve-announce - CVE-2025-21867: bpf, test_run: Fix use-after-free issue in eth_skb_pkt

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Message-ID: <2025032732-CVE-2025-21867-3138@gregkh>
Date: Thu, 27 Mar 2025 14:38:33 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2025-21867: bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type()

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

bpf, test_run: Fix use-after-free issue in eth_skb_pkt_type()

KMSAN reported a use-after-free issue in eth_skb_pkt_type()[1]. The
cause of the issue was that eth_skb_pkt_type() accessed skb's data
that didn't contain an Ethernet header. This occurs when
bpf_prog_test_run_xdp() passes an invalid value as the user_data
argument to bpf_test_init().

Fix this by returning an error when user_data is less than ETH_HLEN in
bpf_test_init(). Additionally, remove the check for "if (user_size >
size)" as it is unnecessary.

[1]
BUG: KMSAN: use-after-free in eth_skb_pkt_type include/linux/etherdevice.h:627 [inline]
BUG: KMSAN: use-after-free in eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165
 eth_skb_pkt_type include/linux/etherdevice.h:627 [inline]
 eth_type_trans+0x4ee/0x980 net/ethernet/eth.c:165
 __xdp_build_skb_from_frame+0x5a8/0xa50 net/core/xdp.c:635
 xdp_recv_frames net/bpf/test_run.c:272 [inline]
 xdp_test_run_batch net/bpf/test_run.c:361 [inline]
 bpf_test_run_xdp_live+0x2954/0x3330 net/bpf/test_run.c:390
 bpf_prog_test_run_xdp+0x148e/0x1b10 net/bpf/test_run.c:1318
 bpf_prog_test_run+0x5b7/0xa30 kernel/bpf/syscall.c:4371
 __sys_bpf+0x6a6/0xe20 kernel/bpf/syscall.c:5777
 __do_sys_bpf kernel/bpf/syscall.c:5866 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5864 [inline]
 __x64_sys_bpf+0xa4/0xf0 kernel/bpf/syscall.c:5864
 x64_sys_call+0x2ea0/0x3d90 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xd9/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 free_pages_prepare mm/page_alloc.c:1056 [inline]
 free_unref_page+0x156/0x1320 mm/page_alloc.c:2657
 __free_pages+0xa3/0x1b0 mm/page_alloc.c:4838
 bpf_ringbuf_free kernel/bpf/ringbuf.c:226 [inline]
 ringbuf_map_free+0xff/0x1e0 kernel/bpf/ringbuf.c:235
 bpf_map_free kernel/bpf/syscall.c:838 [inline]
 bpf_map_free_deferred+0x17c/0x310 kernel/bpf/syscall.c:862
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0xa2b/0x1b60 kernel/workqueue.c:3310
 worker_thread+0xedf/0x1550 kernel/workqueue.c:3391
 kthread+0x535/0x6b0 kernel/kthread.c:389
 ret_from_fork+0x6e/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

CPU: 1 UID: 0 PID: 17276 Comm: syz.1.16450 Not tainted 6.12.0-05490-g9bb88c659673 #8
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-3.fc41 04/01/2014

The Linux kernel CVE team has assigned CVE-2025-21867 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 5.18 with commit be3d72a2896cb24090f268dce4aa8a304d40bc23 and fixed in 6.1.130 with commit f615fccfc689cb48977d275ac2e391297b52392b
	Issue introduced in 5.18 with commit be3d72a2896cb24090f268dce4aa8a304d40bc23 and fixed in 6.6.80 with commit d56d8a23d95100b65f40438639dd82db2af81c11
	Issue introduced in 5.18 with commit be3d72a2896cb24090f268dce4aa8a304d40bc23 and fixed in 6.12.17 with commit 972bafed67ca73ad9a56448384281eb5fd5c0ba3
	Issue introduced in 5.18 with commit be3d72a2896cb24090f268dce4aa8a304d40bc23 and fixed in 6.13.5 with commit 1a9e1284e87d59b1303b69d1808d310821d6e5f7
	Issue introduced in 5.18 with commit be3d72a2896cb24090f268dce4aa8a304d40bc23 and fixed in 6.14 with commit 6b3d638ca897e099fa99bd6d02189d3176f80a47

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-21867
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	net/bpf/test_run.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f615fccfc689cb48977d275ac2e391297b52392b
	https://git.kernel.org/stable/c/d56d8a23d95100b65f40438639dd82db2af81c11
	https://git.kernel.org/stable/c/972bafed67ca73ad9a56448384281eb5fd5c0ba3
	https://git.kernel.org/stable/c/1a9e1284e87d59b1303b69d1808d310821d6e5f7
	https://git.kernel.org/stable/c/6b3d638ca897e099fa99bd6d02189d3176f80a47